The invention relates to explosive separation joint systems such as utilized for separation of launch vehicles. Such joints utilize mild detonating fuses (MDF) that extend from the separable portions into a detonation manifold and are initiated by an external initiating ordnance such as flexible confined detonating cord also extending into the detonation manifold. The MDF having an end with a booster attached thereto. The initiating ordnance positioned to provide an impulse perpendicularly to the axis of the MDF and being in alignment with the MDF booster. The MDF may be in a flattened steel tube and upon detonation of the MDF by the initiating ordnance the steel tube expands to a circular cross sectional configuration that ruptures or causes disengagement of separable portions of the joint allowing separations of portions of a launch vehicle or spacecraft. Any operational failure of such joint separating portions can be expected to be catastrophic to the mission. Any reduction in the risk of failure of such joints would be appreciated by the industry.